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A carbohydrate component of plant cell walls; associated with sieve plates where calluses are formed.
Having hardened protuberances, as on the skin or on leaves and stems.



a polysaccharide, insoluble in water, contained in plants and consisting of glucose-molecule residues joined in a spiral chain (as opposed to cellulose, in which the glucose molecules are joined in a straight chain).

Callose lines the tubules of the sievelike layers of phloem; asthese tubules age, the amount of callose increases and the tubulesbecome plugged and cease functioning. When a plant is injured, callose is deposited on the cell walls of the parenchyma, forminga callus. Callose is also found in the cell walls of some algae andfungi.

References in periodicals archive ?
Callose deposition has been used as an indicator of Al-induced stress because it accumulates in root tips after exposure to toxic levels of Al (Wissemeier et al.
Furthermore, callose accumulation was also examined in the pineapple root tips to determine whether increased Al tolerance resulted in reduced callose accumulation after exposure to Al.
striata numerous cytoplasmic connections are observed while the callose wall starts to form and the primary wall is still present.
In the present study, the foot layer and endexine are also formed simultaneously and concomitant with the callose wall dissolution.
At the transition from archesporial cells to sporocytes in mosses and hornworts, special expandable walls of callose or mucopolysaccharide are formed within the vegetative cell walls.
depolarization and callose formation in the outer cortical cells of the
Tritici: Association of the hypersensitive reaction with the cellular accumulation of linkin-like material and callose.
As the pollen mother cells separate and develop callose walls, the cell walls of the tapetal cells degenerate and plasmodesmata develop connecting the protoplasts [ILLUSTRATION FOR FIGURES 12, 13 OMITTED].
Heslop-Harrison (1968b) stated that orbicules cannot be considered to act as a temporary storage of sporopollenin material because they are neither eliminated nor eroded during exine growth after callose dissolution.
This inner cortex - containing glycoproteins, callose, glucanase, chitinase, peroxidase, lignin-like products, and astorbate and dehydroascorbate reductase - is considered to serve as both a defense and as an oxygen diffusion barrier (Staehelin et al.
She studied the seasonal changes in healthy and infected plants and determined that in the spring, when winter accumulations of callose are removed from blocked sieve areas, the tissue is reactivated.
They also noted that, at certain concentrations, Calcofluor White (a fluorochrome specific for cellulose) induced the production of large deposits of what might be callose at the tips of root hairs.